Commitments and contingencies (Tables)

12 Months Ended

Dec. 31, 2012

Commitments and contingencies

Schedule of operating lease expense

	Year ended December 31,
	2012		2011		2010
Operating lease expense	$	1,515,189	$	1,396,122	$	1,243,621

Schedule of future minimum rental payments under noncancelable operating leases

Years ending December 31,
2013	$	1,455,730
2014	1,013,123
2015	926,702
2016	877,000
2017	—
Thereafter	—
Total minimum lease payments	$	4,272,555

Schedule of leased property under capital leases

	December 31,
	2012			2011
Computer hardware	$	882,246		$	1,048,575
Less: Accumulated depreciation	(257,615		)	(531,949		)
Total capital leases, net	$	624,631		$	516,626

Schedule of future minimum rental payment under capital leases

Years ending December 31,
2013	$	376,336
2014	260,086
2015	116,969
2016	4,843
2017	—
Thereafter	—
Total minimum lease payments	758,234
Less: Amounts representing taxes, included in total minimum lease payments(*)	—
Net minimum lease payments	758,234
Less: Amounts representing interest payments	(56,636		)
Present value of net minimum lease payments	$	701,598

* Tax amounts related to capital lease payments are inconsequential.

Schedule of future minimum payments under those agreements

Years ending December 31,
2013	$	340,000
2014	300,000
2015	300,000
2016	25,000
2017	—
Thereafter	—
Total payments	$	965,000